Near Testing

The purpose of determining a near Rx is to provide a correction that renders vision clear and comfortable at the desired near distance

  • Usually is in the form of plus over the distance refraction

Near tests are used in order to determine a patient’s accommodative ability and/or range

  • Example: tentative near add for a presbyopic patient or a young patient with reduced accommodative ability

May also be used to correlate data and to diagnose problems such as latent hyperopia, accommodative spasm and vergence problems

Patient may have symptoms of: blurring when reading and/or changing fixation distance, fatigue, headaches or brow aches, diplopia, “arms too short,” and burning or stinging

Patient’s adaptations/solutions may include: decreasing near activities, brighter lighting, arm stretching, allow slight blurring, live with the discomfort, use cheater glasses/magnifier, squinting and drowsiness

Factors influencing near vision and/or near Rx include:

  • Amplitude of accommodation
  • Lag/lead of accommodation
  • Accommodative spasm
  • Accommodative facility
  • Phorias
  • Vergences
  • Refractive error

Methods of determining a tentative near add (TNA)

  • NRA/PRA

Negative Relative Accommodation: the patient’s ability to relax accommodation relative to the vergence system

Positive Relative Accommodation: the patient’s ability to accommodate relative to the vergence system

  • Use BVA or manifest refraction and PD on near setting
  • Target: 20/20 line or 20/20 block of letters on rotary chart at 40cm
  • Use overhead lighting with stand lamp on target
  • To determine NRA:
  • Confirm that the patient can see the letters clearly (if blurry, add plus binocularly until clear)
  • Instruct patient to let you know “when the letters first start to blur”; add plus binocularly [0.25D steps] until first sustained blur
  • Record LIP (lens in place when endpoint is reached) and net NRA (usually a net plus value)
  • Net NRA= net plus added binocularly to the MPBVA until first sustained blur (i.e., the difference between LIP and the patient’s starting point)
  • Interpretation of NRA test:
  • With each click of plus added, the patient must relax out accommodation by that amount
  • When the accommodation is relaxed the eyes also automatically diverge some
  • In order to continue to seeing a single image, the eyes must converge to compensate for this divergence
  • Limiters of the NRA test are the patient’s ability to relax out accommodation and/or the ability to converge (whichever comes first)
  • To determine PRA:
  • The starting point of the PRA test is the endpoint of NRA
  • Instruct patient to let you know “when the letters first start to blur”; add minus binocularly (decrease the plus) [0.25D steps] until first sustained blur
  • Record LIP (lens in place when the endpoint is reached) and net PRA (usually a net minus value)
  • Note: For presbyopic patients or patients with low amplitudes the net PRA may be a positive value, indicating that with the M1 in place alone, the target was blurry
  • Net PRA= net minus added binocularly to the MPBVA until first sustained blur (i.e., the difference between LIP and the patient’s starting point)
  • Interpretation of PRA test:
  • With each click of minus added, the patient must accommodate by that amount
  • When the accommodation is stimulated the eyes also automatically converge some
  • In order to continue to seeing a single image, the eyes must diverge to compensate for this convergence
  • Limiters of the PRA test are the patient’s ability to accommodate(i.e., accommodative amplitude) and/or the ability to diverge (whichever comes first)
  • Calculate a tentative near add based on NRA/PRA
  • Endpoints: first sustained blur
  • First sustained blur: the point at which the patient’s image becomes more blurry that it was initially and remains blurry despite efforts to clear it
  • Target may still be distinguishable
  • Blur out: the point at which the patient’s image becomes so blurry that he/she is unable to distinguish the target
  • TNA=sum of both net endpoints divided by 2
  • The real add could be different due to other factors such as working distance, lighting conditions, size of task and refractive error
  • Expected values
  • NRA: +2.00 to +2.50 (for any patient)
  • PRA: -2.37 to -3.37 (pre-presbyopic)
  • Determine binocular amplitude of accommodationwith the PRA
  • Patient must be accommodating 2.50D if he/she is able to see the target clearly at 40 cm with M1 in place
  • If PRA net is a minus value:
  • Patient accommodated 2.50 for the test stimulus plus whatever minus you were able to add over M1 during PRA
  • Add net PRA to 2.50D
  • If PRA net is a plus value:
  • Patient likely was unable to see the target at 40cm clearly initially (he/she likely required that you add plus before beginning the test in order to see it clearly)
  • Take away net PRA from 2.50D
  • Fused Cross Cylinder (FCC)
  • Use BVA or manifest refraction and PD on near setting
  • Target: cross grid on rotary chart at 40 cm
  • Use dim lighting on card
  • Dial in +/- 0.50 on strong sphere auxiliary wheel knob
  • +0.50D @ 090/ -0.50D @180 +0.50 -1.00 x 090
  • Forms a 1.00D astigmatic interval
  • Minus cylinder axis vertical vertical line is posterior to horizontal line focus
  • Confirm that the patient can see the grid (“lines up and down and lines side to side”)
  • Ask patient “which set of lines appear darker, up and down or across”
  • If “equal” or horizontal lines are darker: add plus until vertical is darker
  • ALWAYS start with vertical darker in order to gain control of accommodation
  • If vertical: add minus (decrease plus) binocularly until horizontal and vertical lines are equally dark or reversal (i.e., horizontal)
  • When reverses from vertical to horizontal, your endpoint is the last vertical
  • Add in one click of plus when patient reports reversal
  • Record LIP and Net
  • The difference between the MPBVA and the LIP is the tentative near add
  • The horizontal lines will be darker if the patient is under accommodated----LAG of accommodation
  • The vertical lines will be darker if the patient is over accommodated----LEAD of accommodation
  • The lines will be equally dark if the patient is accurately accommodated
  • Expected lag of accommodation: +0.50 + 0.50 (for non-presbyopes)
  • Esophoria and accommodative limits/fatigue could cause the lag to be greater
  • More patient accommodates more eso
  • Exophoria and spasms of accommodation could cause the lag to be lower
  • More patient accommodates less exo
  • One-half amplitude in reserve
  • Determine ½ amplitude of accommodation and accommodative stimulus (determined by working distance)
  • What do you have to give them so that ½ of their amps plus the patient’s add= stimulus?
  • Plus Build Up
  • The least amount of plus that gives the patient noticeably “better” vision at near
  • “better” means that the patient subjectively reported that it was better (does not require that he/she read additional letters)
  • Use BVA or manifest refraction and PD on near setting
  • Target: 20/20 line or 20/20 block of letters on rotary chart at 40cm
  • Use overhead lighting with stand lamp on target
  • To determine:
  • Confirm that the patient can see the letters clearly (if blurry, add plus binocularly until clear)
  • Explain to the patient that you are going to add lenses until the target is as clear as possible
  • Add plus binocularly until letters first appear legible and continue to add plus until patient preference is identified/ no further improvement (ask “better here or about the same”)
  • If better: add more plus
  • If about the same: back up one this is your endpoint
  • Net=TNA
  • Measure range of clear vision
  • Ideal is 1/3 IN and 2/3 OUT
  • Minus Lens Amplitudes of Accommodation
  • The accommodative demand of the small near point target is changed in a stepwise fashion as minus lenses are introduced to the patient monocularly
  • Use BVA or manifest refraction and PD on near setting
  • Target: a row of letters 1 or 2 lines larger than their best near acuity on rotary chart at 40cm
  • Use overhead lighting with stand lamp on target
  • To determine:
  • Occlude OS
  • Confirm that the patient can see the letters clearly (if blurry, add plus binocularly until clear)
  • Add minus lenses (or reduce plus) [-0.25 D steps], allowing up to ~5-10 seconds for the patient to clear the letters
  • Continue to add lenses until the patient reports that the letters are blurry and remain blurry= first sustained blur
  • Repeat for OS
  • The amount of minus added to your patient’s Rx plus 2.50D (stimulus for near card) is the total amplitude of accommodation
  • Age Tables

AGE / ADD
40 / +0.75
42 / +1.00
44 / +1.25
46 / +1.50
48 / +1.75
50 / +2.00
52 / +2.25
54 / +2.50
  • Hoffstetter’s Formula
  • Minimum Expected Amp: 15- 0.25 (age)
  • To finalize the add
  • Have patient assume a normal reading position (without phoropter)
  • Place the TNA in a trial frame or over Rx to demonstrate range and clarity
  • Can compare with +/- 0.25 D change
  • The ideal range should be 1/3 IN and 2/3 OUT (dioptric midpoint)
  • Educate the patient about choices, expectations, adaptation, and limitations
  • Increasing the add decrease depth of focus
  • Consider the patient’s vocation and avocation requirements (may need more than one Rx)

Presbyopia “old sight”

  • Incipient presbyopia: when symptoms first appear
  • Premature presbyopia: symptoms appear before expected
  • Manifest presbyopia: some remaining accommodation
  • Absolute presbyopia: none remaining (bottomed out)
  • Myopes usually move into presbyopia later
  • Myopes accommodative demand is less in spectacles than with CLs
  • Hyperopes accommodative demand is less in CLs than with spectacles
  • In spectacles, myopes have less accommodative demand than do hyperopes