Comparison of ocular biometric parameters between nanophthalmos and primary angle closure disease: a cross-sectional comparative study

Purpose To compare the ocular biometric parameters between eyes with nanophthalmos and primary angle closure disease (PACD). Methods This was a cross-sectional, comparative hospital-based study. A total of 144 subjects (144 eyes) including 58 nanophthalmos patients and 86 primary angle closure disease (26 primary angle closure and 60 primary angle closure glaucoma) patients were included in the study. The parameters studied were central corneal thickness (CCT), anterior chamber depth (ACD), anterior chamber angle (ACA), angle opening distance (AOD500 &AOD750), lens vault (LV), lens thickness (LT), axial length (AL), lens axial factor (LAF), relative lens position (RLP), and retinochoroido-scleral (RCS) thickness. All measurements were obtained prior to any laser or surgical intervention. Results The mean +/- SD age was comparable without any statistically significant difference across all the groups (57.3 +/- 11 years in the nanopthalmos group,56.7 +/- 9.3 years in the PAC group,56.1 +/- 9.2 in the PACG group).The median IOP was highest in PAC eyes (17mmHg) followed by PACG eyes (16mmHg) and nanophthalmic eyes (14mmHg) (p = 0.003). A significant difference was found in ACA among the three groups (p = 0.003), PAC and PACG eyes exhibited wider angles (median 26 degrees for each) whereas nanophthalmic eyes showed narrower angle (median 20.5 degrees). The median AL was highest in PACG eyes, intermediate in PAC eyes and shortest in nanophthalmic eyes (p < 0.001). Similarly, median ACD was shallower in nanophthalmic eyes compared with PAC and PACG eyes(p = 0.0001). RCS thickness was significantly greater in nanophthalmos (similar to 2.0 mm) compared to PAC and PACG (similar to 1.5 mm), highlighting its diagnostic value. No difference was found in LT(p = 0.879) or CCT(p = 0.434) between the groups. Nanophthalmic eyes had higher LV, greater RCS thickness, higher LAF and normal RLP, compared to PAC and PACG. Conclusion Nanophthalmos represents a more anatomically crowded and complex entity compared to PACD, characterized by critical biometric alterations that predispose to severe angle closure. Comprehensive biometric evaluation is essential for early diagnosis, risk stratification, and individualized management planning in these eyes.